Igniter

ABSTRACT

An igniter, an ignition method and a method of assembling an ignitor are provided. In one embodiment, the igniter includes a first member having an inner surface. The igniter also includes a second member having an outer surface engaged with the inner surface when in an assembled configuration and forming a space between the inner surface and the outer surface. The igniter further includes an ignition charge disposed in the space. The second member is configured to move with respect to the first member when in the assembled configuration so as to apply a predetermined pressure, which includes a shear force and a compressive force, to the ignition charge to ignite the ignition charge. According to various embodiments, ignition of the ignition charge is improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/686,071, filed on Aug. 24, 2017, and claims thebenefit under 35 U.S.C. §§ 120 and 365 of PCT Application No.PCT/JP2016/055375, filed on Feb. 24, 2016, which is hereby incorporatedby reference. PCT/JP2016/055375 also claimed priority from JapanesePatent Application No. 2015-035593 filed on Feb. 25, 2015, the entirecontents of which are incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to an igniter.

BACKGROUND ART

A pyrotechnic actuator mechanism, which is an actuator mechanism toobtain an output by moving a piston by means of the force of an ignitioncharge, is used for apparatuses including, for example, an airbag systemfor vehicles, a pedestrian protection system, a current breaker, aperforator, and a fire extinguishing system. Further, a syringe, whichdischarges or injects an injection objective substance by means of apressurized piston, is also known in the field of medical treatment. Apyrotechnic actuator mechanism is widely investigated as a drivingsource for the syringe as described above. An igniter, which ignites anignition charge, is carried as a driving source to obtain an output inthe actuator mechanism as described above.

In this context, the igniter has been hitherto widely developed. Whenthe igniter is roughly classified, there are an electric type igniterand a mechanical type igniter. In the case of the electric type igniter,the ignition charge is electrically ignited by means of an ignitioncurrent supplied from the outside. The supply of the ignition current iscontrolled relatively easily. Further, the ignition current can besupplied to a large number of igniters at once. Therefore, the electrictype igniter is especially useful when it is intended to arbitrarilycontrol the ignition of each of the igniters in a system which includesa large number of the igniters. On the contrary, the electric typeigniter requires, for example, a power source for supplying the ignitioncurrent and a control device for controlling the supply. It isinevitable that the system is large or complicated.

On the other hand, in the case of the mechanical type igniter, theenergy for igniting the ignition charge is obtained from any mechanicalmotion or operation not from the ignition current. For example, asdescribed in Switzerland Patent Publication No. 681175, the frictionforce is generated between a friction member 7 and a first ignitioncharge 8 by pulling out a pin 12. The first ignition charge 8 is ignitedby the energy thereof, and propellants or explosives 6, 15 aresuccessively combusted. Further, as in a syringe described in U.S. Pat.No. 6,537,245, an end portion 8 of a friction member 11 is rubbed withan ignition charge 2 in accordance with a depressing operation fordepressing a button 3 performed by a user. The ignition charge 2 isignited by the friction energy generated thereby. Then, an injectionsolution is discharged or injected by the combustion energy generated bythe ignition.

SUMMARY Problems to be Solved

In the case of the conventional mechanical type igniter, the ignition ofthe ignition charge is performed by utilizing the friction energygenerated by the relatively linear motion including, for example, thedepression and the pulling out of the friction member performed by theuser. However, the friction force, which acts between the frictionmember and the propellant or explosive in accordance with the linearmotion, easily varies depending on, for example, the state of contactbetween the both. Therefore, it is not easy to appropriately adjust thefriction energy generated by the linear motion as described above. Ifthe friction force between the friction member and the ignition chargeis excessively weak, then any sufficient friction energy is notgenerated, and it is difficult to ignite the ignition charge. On theother hand, if the friction force is excessively strong, then theoperability of the igniter is deteriorated or lowered, or it is fearedthat the igniter may be broken on account of any operation of the user.

Accordingly, in view of the problems described above, an object of thepresent disclosure is to provide a mechanical type igniter whichrealizes preferable ignition of an ignition charge.

Example Means for Solving the Problems

In order to solve the problems as described above, according to thepresent disclosure, a mechanical type igniter has such a structure thata pressure, which includes a shear force (shearing force), is applied toan ignition charge as the energy for igniting the ignition charge, andmade it possible to stably supply the energy for the ignition to theignition charge. Specifically, the present disclosure resides in anigniter comprising a first ignition charge; a first member which has apredetermined inner surface; and a second member which is arranged in astate of being inserted into the first member and which has apredetermined outer surface opposed to the predetermined inner surfacein an arrangement state, for forming a predetermined space to arrangethe first ignition charge between the predetermined inner surface andthe predetermined outer surface. Then, in the igniter, the second memberis arranged in the arrangement state so that the second member isrotatable with respect to the first member about a center of an axis ofinsertion of the second member in the arrangement state, in a state inwhich the first ignition charge is interposed in the predeterminedspace; and the predetermined space has an opening which is communicatedwith outside of the predetermined space in an axial direction of theaxis of insertion. Accordingly, when the second member is rotated withrespect to the first member, then the first ignition charge is ignitedin the predetermined space by means of a predetermined pressureincluding a shear force generated between the predetermined outersurface and the predetermined inner surface in accordance with therotation, and a combustion product of the first ignition charge isreleased from the opening of the predetermined space.

Any ignition charge can be adopted for the first ignition charge whichis used for the igniter according to the present disclosure, providedthat the ignition charge is ignitable when the predetermined pressureincluding the shear force is applied as described above. The ignitioncharge is exemplified, for example, by ZPP (mixture of zirconium andpotassium perchlorate) and black powder (for example, boron saltpeter).Then, the ignition charge is arranged in the predetermined space whichis defined by the predetermined inner surface of the first member andthe predetermined outer surface of the second member. The predeterminedspace is the space which is defined by the both surfaces in thearrangement state formed by inserting the second member into the firstmember. The predetermined space has the opening which is communicatedwith the outside of the predetermined space, in addition to thesurfaces.

Then, in the arrangement state, the second member is in such a statethat the second member is rotatable with respect to the first member.Then, when the second member is rotated with respect to the firstmember, the both members are relatively rotated in the state in whichthe first ignition charge is interposed in the predetermined space. As aresult, both surfaces of the predetermined inner surface and thepredetermined outer surface are relatively moved so that the shear forceis applied to the first ignition charge during the rotational motion. Asa result, the predetermined pressure, which includes the relativelylarge shear force, can be stably applied to the first ignition charge.It is possible to reliably ignite the first ignition charge. Note thatthe combustion product, which is produced by the ignition and thecombustion of the first ignition charge, does not stay in thepredetermined space. The combustion product is released to the outsidevia the opening of the predetermined space. The energy (thermal energyand kinetic energy) of the combustion product released to the outside isthe primary output of the igniter.

In this way, the igniter according to the present disclosure adopts suchan arrangement that the predetermined pressure, which includes the shearforce, is applied to the ignition charge arranged in the predeterminedspace by the aid of the predetermined inner surface and thepredetermined outer surface in accordance with the mechanical motionwhich is the rotational movement of the second member with respect tothe first member. The shear force, which is based on the rotation, makesit possible to stably supply the energy for the ignition to the firstignition charge, as compared with any ignition technique which utilizesthe friction force based on the linear motion as adopted in theconventional technique. Therefore, it is easy to perform the productionmanagement including the management of, for example, the dimensionaltolerance of the parts of the igniter. Further, it is possible torealize the reliable ignition as expected for the igniter.

In this context, the igniter may further comprise a regulating portionwhich regulates separation of the second member from the first member inthe direction of the axis of insertion when the second member is rotatedwith respect to the first member and the first ignition charge isignited. There is such a possibility that the first member and thesecond member may receive the pressure in the directions in which thefirst member and the second member are separated from each other, fromthe combustion product which is produced when the first ignition chargeis ignited in the predetermined space. In view of the above, theseparation of the both is regulated by providing the regulating portion,and it is possible to suppress the igniter from being subjected to thebreakage or the like after the ignition. Note that the regulatingportion regulates the separation of the first member and the secondmember in the axial direction of the axis of insertion in every sense.The regulating portion does not inhibit the rotation of the secondmember with respect to the first member.

In this context, as an example of the regulating portion, the regulatingportion may be the predetermined inner surface and the predeterminedouter surface which are formed to provide protrusion and recess in across section taken in the axial direction of the axis of insertion. Inthis case, when the first ignition charge is ignited, then thepredetermined inner surface and the predetermined outer surface arebrought in contact with each other, and thus the separation of thesecond member from the first member is regulated. That is, thepredetermined inner surface and the predetermined outer surface, whichare arranged to form the protrusion and recess, are engaged or meshedwith each other upon the ignition of the first ignition charge, and thusthe both surfaces function as the regulating portion.

Further, as another example of the regulating portion, when thepredetermined inner surface is a screw thread portion of the firstmember which is a female screw member; and the predetermined outersurface is a screw thread portion of the second member which is a malescrew member; then the regulating portion may be formed by the firstmember and the second member which are screw-engaged with each other.That is, when the first member as the female screw member and the secondmember as the male screw member are screw-engaged with each other, astate is given, in which the screw threads of the both are engaged ormeshed with each other. Therefore, it is possible to regulate theseparation of the both members in the direction of the axis ofinsertion, while the rotation of the second member with respect to thefirst member is sufficiently secured or guaranteed. Note that in thisform, the space, which is provided between the screw thread portions ofthe first member and the second member, is the predetermined space. Whenthe second member is rotated with respect to the first member, thepredetermined pressure including the shear force, which acts between theboth screw thread portions, is applied to the first ignition charge.Accordingly, the ignition thereof is caused.

In this context, the igniter as described above may further comprise asecond ignition charge which is ignitable by the combustion product andwhich is arranged at a predetermined portion capable of being brought incontact with the combustion product of the ignition charge released fromthe opening in the vicinity of the opening of the predetermined space.The first ignition charge is arranged in the predetermined space asdescribed above. Therefore, it is difficult in some cases to increasethe amount of the arranged ignition charge. Further, the ignition isperformed by the predetermined pressure including the shear force in thepredetermined space. Therefore, it may be also difficult to relativelyincrease the amount of the first ignition charge from such a viewpointthat the ignition is preferably performed. On this account, there isalso such a possibility that it is not easy to increase the output asthe igniter by using only the first ignition charge.

In view of the above, the second ignition charge is arranged at theposition which is different from the position of the first ignitioncharge, i.e., at the predetermined portion at which the first ignitioncharge is released. Accordingly, it is possible to raise or enhance theoutput as provided by the igniter. Note that any arbitrary ignitioncharge can be adopted for the second ignition charge, provided that theignition charge is ignitable by the combustion product of the firstignition charge. For example, it is also allowable to adopt an ignitioncharge which has the same quality as that of the first ignition charge,or it is also allowable to adopt an ignition charge which is differentfrom the first ignition charge. Then, preferably, the combustion energy,which is generated by the second ignition charge, is set to be largerthan the combustion energy which is generated by the first ignitioncharge. It is possible to preferably raise the output as the igniter byfurther raising the combustion energy of the second ignition charge asdescribed above.

In this context, the igniter described above may further comprise acommunication passage which is formed for at least one of the firstmember and the second member and which makes communication between thepredetermined space and the predetermined portion at which the secondignition charge is arranged. When the predetermined space and thepredetermined portion are communicated with each other by means of thecommunication passage, then the combustion product of the first ignitioncharge can be thereby delivered smoothly to the second ignition chargewhich is arranged at the predetermined portion, and it is possible tocontemplate the preferred combustion of the second ignition charge.

It is possible to provide the mechanical type igniter which realizespreferable ignition of the ignition charge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic structure of an igniter according to thepresent disclosure.

FIG. 2A illustrates an ignition structure for igniting an ignitioncharge in the igniter shown in FIG. 1.

FIG. 2B illustrates an ignition structure for igniting an ignitioncharge in the igniter shown in FIG. 1.

FIG. 3 shows a schematic structure of an igniter assembly formed byattaching an igniter collar to the igniter shown in FIG. 1.

FIG. 4 shows a schematic structure of a syringe to which the igniterassembly shown in FIG. 3 is attached.

FIG. 5A shows modified embodiments of the igniter according to thepresent disclosure.

FIG. 5B shows modified embodiments of the igniter according to thepresent disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will be explained below withreference to the drawings. Note that the structure or construction ofthe following embodiment is described by way of example, and the presentdisclosure is not limited to the structure or construction of theembodiment.

<Structure of Igniter 10>

FIG. 1 shows a schematic structure of an igniter 10 according to thepresent disclosure. Further, in FIG. 2, a part of the igniter 10 shownin FIG. 1 is enlarged in order to easily grasp the structure in relationto the ignition means for igniting an ignition charge in the igniter 10.Further, FIG. 2A shows a sectional view taken in the direction of theaxis of insertion in relation to the igniter 10 in the same manner asFIG. 1, and FIG. 2B shows a sectional view taken in the directionperpendicular to the direction of the axis of insertion. Note that theaxis of insertion refers to the axis extending in the direction ofinsertion in a state in which a second member 2 is inserted and arrangedwith respect to a first member 1 as described later on in the igniter 10(hereinafter simply referred to as “arrangement state”).

The igniter 10 shown in FIG. 1 is a mechanical type igniter, and theigniter 10 is placed in an arrangement state brought about before afirst ignition charge 8 charged into the inside thereof (see FIG. 2) isignited. Therefore, when the mechanical force is allowed to act from theoutside on the igniter 10 which is placed in this arrangement state, theignition is thereby performed for the first ignition charge 8 chargedtherein. In this arrangement, the main body of the igniter 10 is formedby the first member 1 and the second member 2. The first member 1 has ascrew thread which is formed such that the inner surface thereoffunctions as a female thread at an insertion portion 1 a into which thesecond member 2 is inserted. The inner surface of the first member 1,which is formed by the screw thread of the female screw, is referred toas “screw thread surface 1 c” as depicted in FIG. 2A. The screw threadsurface 1 c corresponds to the predetermined inner surface according tothe present disclosure. On the other hand, the second member 2, which isinserted into the first member 1, has a screw thread which is formedsuch that the outer surface thereof functions as a male thread. Theouter surface of the second member 2, which is formed by the screwthread of the male screw, is referred to as “screw thread surface 2 b”as depicted in FIG. 2A. The screw thread surface 2 b corresponds to thepredetermined outer surface according to the present disclosure.

The first member 1 and the second member 2, which have the screw threadsurfaces 1 c, 2 b as described above, are formed with the respectivescrew thread surfaces so that the first member 1 and the second member 2can be screw-engaged with each other by the aid of the mutual screwthread surfaces. Then, in order to arrive at the arrangement state shownin FIG. 1, the second member 2 is progressively inserted so that thesecond member 2 is advanced from the left side to the right side asviewed in FIG. 1, while slowly rotating and screw-engaging the secondmember 2 with respect to the first member 1. The axis, which extends inthe direction of insertion of the second member 2, is the axis ofinsertion described above. Note that a second ignition charge 4 isarranged in a state provided before the insertion of the second member2, at the portion 1 b (hereinafter referred to as “forward end portion”)disposed on the forward end side of the first member 1 (right side asviewed in FIG. 1). Therefore, the insertion of the second member 2 intothe first member 1 is performed until arrival at the position at whichthe forward end of the second member 2 is brought in contact with thesecond ignition charge 4.

Further, a handle portion 6, which has a sufficient length to such anextent that the handle portion 6 protrudes from the first member 1 evenin a state in which the second member 2 is inserted into the firstmember 1, is attached to a portion of the second member 2 disposed on aproximal end side (left side as viewed in FIG. 1) so that the secondmember 2, which is formed as the male screw member, can be rotated atthe inside of the first member 1. Therefore, the second member 2 isinserted into the first member 1 by rotating the handle portion 6. Notethat a recess 6 a is provided at a central portion of the handle portion6. A part or a tool, which is provided to rotate the handle portion 6,is fitted thereto, making it possible to perform the rotation operationfor rotating the handle portion 6 more easily.

Further, in the arrangement state shown in FIG. 1, the second member 2is attached to the first member 1 after being inserted into the firstmember 1 so that a cup 3 covers the forward end side of the first member1, in other words, the cup 3 covers the second ignition charge 4. Thecup 3 has a top surface 3 b which is arranged opposingly to the secondignition charge 4 and a side surface 3 a which is formed to have anannular form so that the side surface of the first member 1 is coveredtherewith. The top surface 3 b is the portion which is to be cleaved bythe combustion product produced when the igniter 10 is operated. Inorder to cause the cleavage easily, it is possible to form a fragileportion having a strength weaker than those of the surroundings. Then,the side surface 3 a of the cup 3 and the first member 1 are fixed bymeans of the welding. In FIG. 1, the welding portion is referred to byreference numeral 5. Note that the welding portion 5 is formed in anannular form between the side surface 3 a of the cup 3 and the firstmember 1 in order to suppress the invasion of moisture into the igniter10 which would be otherwise caused on account of the welding. Note thatanother method is also available as the technique to fix the cup 3. Thatis, a protruding portion is provided on the inner side of the sidesurface 3 a of the cup 3, the protruding portion is fitted into a recessprovided on the side surface of the first member 1, and thus the firstmember 1 is fixed to the cup 3. In this case, in order to avoid theinvasion of moisture, it is preferable to apply a sealing agent betweenthe side surface 3 a and the first member 1. Further, when the cup issubjected to the fitting by means of the protruding portion and therecess as described above, it is preferable to determine the shapes andthe sizes of the protruding portion and the recess so that the cup 3 isnot disengaged by the pressure generated by the combustion of therespective ignition charges.

An explanation will now be made about the charge of the first ignitioncharge 8 in the igniter 10. As shown in FIG. 2A, a minute space 7 isformed between the first member 1 and the second member 2 which are in arelationship of being screw-engaged with each other. That is, in thearrangement state, the screw thread surface 1 c as the inner surface ofthe first member 1 and the screw thread surface 2 b as the outer surfaceof the second member 2, which are opposed to one another, are not insuch a state that the mutual surfaces are completely brought in contactwith each other. Microscopically, as shown in FIG. 2A, the space 7 isformed to such an extent that particles or granules of the firstignition charge 8 can be charged. Therefore, the screw engagementrelationship between the first member 1 and the second member 2 is notprovided to generate the fastening force brought about by the screwengagement, but the screw engagement relationship is provided in orderthat the space is formed to such an extent that the first ignitioncharge 8 can be charged and the second member 2 can be inserted into thefirst member 1 in accordance with the screw engagement. Note that whenthe first ignition charge 8 is charged into the space, the firstignition charge 8 may be charged after preparing a slurry form (wetcharge) while avoiding any dry state of the first ignition charge 8. Forexample, as described in Japanese Patent Application Laid-Open No.2004-115001, an ignition charge can be charged in accordance with such amethod that the ignition charge is dissolved in a solvent to prepare aslurry form, the preparation is poured into the space, and then thesolvent is dried.

In this context, the space 7, which is formed between the screw threadsurface 1 c and the screw thread surface 2 b, is the space in which thefirst ignition charge 8 is charged as described above. The space 7 isformed to surround the second member 2. In this arrangement, the space 7is open to the side of the forward end portion 1 b of the first member 1and the side of the proximal end portion respectively. Then, the openingof the space 7, which is disposed on the side of the forward end portion1 b, is in a state of being closed by the second ignition charge 4arranged at the forward end portion 1 b as shown in FIG. 2A.

Further, as shown in FIG. 2B, a groove 9, which extends in the directionof the axis of insertion described above, is formed for the secondmember 2. The groove 9 has a predetermined depth, and the groove 9 isopen to the space 7 which is formed between the screw thread surface 1 cand the screw thread surface 2 b. Further, the groove 9 is alsoconnected to the space disposed on the side of the forward end portion 1b at which the second ignition charge 4 is arranged. That is, the groove9 is formed so that the space 7 and the space disposed on the side ofthe forward end portion 1 b are communicated with each other.

An explanation will be made about the ignition operation of the igniter10 constructed as described above. Note that in this embodiment, theignition charges, which have the same components, are used for the firstignition charge 8 and the second ignition charge 4. The ignition chargeis exemplified, for example, by a propellant containing zirconium andpotassium perchlorate (ZPP), a propellant containing titanium hydrideand potassium perchlorate (THPP), a propellant containing titanium andpotassium perchlorate (TiPP), a propellant containing aluminum andpotassium perchlorate (APP), a propellant containing aluminum andbismuth oxide (ABO), a propellant containing aluminum and molybdenumoxide (AMO), a propellant containing aluminum and copper oxide (ACO), apropellant containing aluminum and iron oxide (AFO),or a propellantcomposed of a combination of a plurality of the foregoing propellants.These propellants exhibit such characteristics that, although thepropellants generate hot and high-pressure plasma during combustionimmediately after ignition, when combustion products condense at a roomtemperature, the propellants do not contain gaseous components and thepressure generated decreases abruptly. It is also allowable that anypropellant or pyrotechnic charge other than the above is used as theignition charge.

In this context, when the handle portion 6 is rotated at a strengthwhich is intense to a certain extent in the arrangement state shown inFIG. 1, the second member 2 is further screw-engaged in the first member1 in the state in which the first ignition charge 8 is charged in thespace 7. In this situation, the screw thread surface 1 c disposed on theside of the first member 1 and the screw thread surface 2 b disposed onthe side of the second member 2 are progressively moved relatively toone another so that the predetermined pressure, which includes the shearforce and the compressive force, is applied to the first ignition charge8 charged in the space 7. In particular, the relatively large shearforce can be generated by rotating the second member 2. It is possibleto supply the energy which is sufficient to ignite the first ignitioncharge 8 charged in the space 7.

When the predetermined pressure is applied to the first ignition charge8 in accordance with the rotation of the second member 2 as describedabove, then the first ignition charge 8 is ignited, and the combustionproduct is produced by the combustion thereof. In this case, the space7, in which the first ignition charge 8 is arranged, is open to thespace disposed on the side of the forward end portion 1 b at which thesecond ignition charge 4 is arranged. Therefore, the combustion productflows into the side of the second ignition charge 4 via the opening.Further, as described above, the second member 2 is formed with thegroove 9. Therefore, the combustion product, which is produced in thespace 7, flows into the side of the second ignition charge 4 via thegroove 9 as well. In this way, the combustion product, which is producedby the ignition and the combustion of the first ignition charge 8, issupplied to the second ignition charge 4, and thus the second ignitioncharge 4 is subsequently ignited and combusted. As for the secondignition charge 4, a relatively large space, in which the secondignition charge 4 is arranged, can be secured as compared with the firstignition charge 8. Therefore, the charge amount of the second ignitioncharge 4 is an amount to such an extent that the output is determined asprovided by the igniter 10. Therefore, the charge amount of the firstignition charge 8 is an amount capable of producing the combustionproduct in order to ignite and combust the second ignition charge 4.

As described above, in the igniter 10, the predetermined pressureincluding the shear force is applied to the first ignition charge 8charged in the space 7 in accordance with the mechanical rotationalmotion of the second member 2 brought about as the starting point.Accordingly, the first ignition charge 8 and the second ignition charge4 are successively ignited and combusted, and the output is obtained asthe igniter 10. Then, it is possible to secure or guarantee the stableignition and the combustion of the ignition charge by utilizing theshear force resulting from the rotational motion as described above.Note that when the first ignition charge 8 and the second ignitioncharge 4 are combusted, the pressure, which corresponds to thecombustion energy, is applied to the second member 2. However, thesecond member 2 is screw-engaged with the first member 1. Therefore,when the pressure is applied, the screw thread surface 1 c and the screwthread surface 2 b are engaged or meshed with each other. The separationof the second member 2 from the first member 1 (for example, themovement in the leftward direction as viewed in FIG. 1) is regulated.

<Example of Use of Igniter 10>

In this context, when the igniter 10 is carried on a predeterminedapparatus or device, the output thereof can be thereby utilized for avariety of purposes. Accordingly, an explanation will be made on thebasis of FIG. 3 about an igniter assembly 15 which is formed byattaching an igniter collar 11 to the igniter 10 in order to easilyutilize the output of the igniter 10. The igniter collar 11 is a memberwhich is provided in order that the igniter 10 is attached and fixed toone side (right side as viewed in FIG. 3) of a base plate 11 b includinga through-hole 11 a formed at the center. Then, the handle portion 6 isarranged by the aid of the through-hole 11 a on the other side (leftside as viewed in FIG. 3) of the base plate 1 b in a state in which therecess 6 a is exposed. Note that the igniter 10 is fixed by a resin 12with respect to the igniter collar 11. The rotational motion of thehandle portion 6 is secured or guaranteed in the fixed state.

When the igniter 10 is attached to the igniter collar 11 as describedabove, the igniter 10 is easily carried on the side of the predeterminedapparatus or device by the aid of the igniter collar 11. Further, in theigniter assembly 15, the handle portion 6 and the components or partsrelevant to the ignition charge charged in the igniter 10 are arrangedwith the base plate 11 b intervening therebetween. Therefore, thecombustion product of the ignition charge, especially the combustionproduct of the first ignition charge 8 hardly arrives at the side of thehandle portion 6. The combustion product hardly affects the operation ofthe igniter 10, i.e., for example, the operation to rotate the handleportion 6 performed by the user in order to cause the ignition. Thisfeature also improves the operability of the igniter 10 operated by theuser.

An explanation will now be made on the basis of FIG. 4 about aneedleless syringe 20 which carries the igniter assembly 15 shown inFIG. 3. FIG. 4 shows a sectional view of the syringe 20. The right sideof FIG. 4 is the forward end side of the syringe 20, i.e., the side onwhich an injection solution is discharged or injected. The left side ofFIG. 4 is the proximal end side of the syringe 20, i.e., the side onwhich the user operates the syringe 20. The syringe 20 has a mainsyringe body 22. A through-hole 29, which extends in the axial directionand which has a constant diameter in the axial direction, is provided ata central portion of the main syringe body 22. Then, one end of thethrough-hole 29 is communicated with a combustion chamber 28 which has adiameter larger than the diameter of the through-hole 29. The remainingother end of the through-hole 29 arrives at a nozzle 24. Further, theigniter assembly 15 is installed on the side of the combustion chamber28 opposite to the communication portion communicated with thethrough-hole 29 so that the top surface 3 b of the cup 3 is opposed tothe communication portion.

In this case, any additional ignition charge is not especially arrangedin the combustion chamber 28 shown in FIG. 4. However, for example, agas generating agent, which is combusted by the combustion product ofthe ignition charge to generate the gas, can be also arranged in thecombustion chamber 28. As for an example of the gas generating agent, itis possible to exemplify a single base smokeless propellant including98% by mass of nitrocellulose, 0.8% by mass of diphenylamine, and 1.2%by mass of potassium sulfate. Further, it is also possible to usevarious gas generating agents used for a gas generator for airbags and agas generator for seat belt pretensioners. The combustion completiontime can be changed for the gas generating agent by adjusting thedimension, the size, and the shape, especially the surface shape of thegas generating agent when the gas generating agent is arranged in thecombustion chamber 28. Accordingly, the pressure transition in thecombustion chamber 28 can be a desired transition.

In the next place, a piston 26 made of metal is arranged in thethrough-hole 29 so that the piston 26 is slidable in the axial directionin the through-hole 29. One end thereof is exposed on the side of thecombustion chamber 28, and a plunger 27 is integrally attached to theother end. In this arrangement, for example, butyl rubber and siliconrubber can be adopted as the material for the plunger 27. Further,examples of the material include styrene-based elastomer, hydrogenatedstyrene-based elastomer, and the styrene-based elastomer and thehydrogenated styrene-based elastomer added with polyethylene,polypropylene, polybutene, polyolefin such as a-olefin copolymer, liquidparaffin, oil such as process oil, and powder inorganic matters such astalc, cast, and mica. Further, polyvinyl chloride-based elastomer,olefin-based elastomer, polyester-based elastomer, polyamide-basedelastomer, and polyurethane-based elastomer, various rubber materials(in particular, those subjected to vulcanization) such as naturalrubber, isoprene rubber, chloroprene rubber, nitrile-butadiene rubber,and styrene-butadiene rubber, mixtures of the kinds of elastomer and thekinds of rubber, and the like can be adopted as the material of theplunger. Further, the plunger 27 has a plurality of annular projectionswhich are formed on the outer circumference of a columnar body. Theprojections are made of resin, and hence the projections are elasticallydeformed when the plunger 27 is inserted into the through-hole 29together with the piston 26. It is possible to enhance the degree oftight contact between the plunger 27 and the inner wall surface of thethrough-hole 29.

Then, the injection solution ML, which is to be injected by the syringe20, is accommodated in the space which is formed in the through-hole 29disposed on the side of the forward end of the syringe as starting fromthe plunger 27. Note that as shown in FIG. 4, the injection solution MLis not enclosed in a completely closed space, and the forward end sideof the syringe is in an open state. However, the inner diameter of thethrough-hole 29 for accommodating the injection solution ML is extremelysmall, and the amount of the injection solution is small as well.Therefore, even when the accommodating space for accommodating theinjection solution ML is the semi-closed space as described above, thestate, in which the injection solution ML is accommodated in thethrough-hole 29, is preferably retained by the surface tension of theinjection solution ML. Then, as described later on, the accommodatedinjection solution ML is pressurized by the output of the igniterassembly 15, and thus the injection solution ML is discharged orinjected from the nozzle 24.

Further, a holder 25, which is formed with a nozzle 24 for dischargingor injecting the injection solution ML, is provided on the forward endside of the syringe 20. The holder 25 is fixed to the end surface of themain syringe body 22 while interposing a gasket 23 by the aid of aholder cap 30. The holder cap 30 is formed to have a brim-shaped crosssection so that the holder cap 30 is caught or hooked by the holder 25,and the holder cap 30 is screw-fixed to the main syringe body 22.Accordingly, the holder 25 is prevented from being disengaged from themain syringe body 22, which would be otherwise disengaged by thepressure applied to the injection solution ML upon the discharge orinjection of the injection solution ML. Further, the igniter assembly 15is also rigidly attached to the main syringe body 22 by means of a cap31 provided therefor, and the igniter assembly 15 is prevented frombeing disengaged. Note that one nozzle 24 may be formed at the center ofthe holder 25, or a plurality of nozzles 24 may be formed.

In this arrangement, as for the syringe 20, an operation button 21 isattached to the recess 6 a (see FIG. 3) exposed on the igniter assembly15. A known mechanical mechanism (for example, a drum cam or the like),which converts the rectilinear motion into the rotational motion, isincorporated into the operation button 21. When the user exerts theforce in order to depress the operation button 21 (the upward in FIG. 4is the depressing direction), the operation button 21 is progressivelydepressed while being rotated by means of the mechanical mechanism. As aresult, the depressing operation to depress the operation button 21causes the rotational motion of the handle portion 6 of the igniterassembly 15.

In the case of the syringe 20 constructed as described above, the userdepresses the operation button 21 in a state in which the forward end ofthe nozzle 24 is brought in contact with a target (for example, skinsurface of arm or leg of the user) into which the injection solution MLis to be injected. In accordance with the operation of the user, thehandle portion 6 of the igniter assembly 15 performs the rotationalmotion (provided that the load is also applied to the handle portion 6in the depressing direction). The first ignition charge 8 is ignited andcombusted by means of the predetermined pressure including the shearforce generated between the screw thread surfaces 1 c, 2 b. After that,the second ignition charge 4 is subsequently ignited and combusted. As aresult, the interior of the combustion chamber 28 is filled with thecombustion product, and the pressure is applied to the injectionsolution ML accommodated in the through-hole 29 by the aid of the piston26. The pressurized injection solution ML is discharged or injectedtoward the injection target via the nozzle 24. The pressure is appliedto the discharged injection solution ML. Therefore, the injectionsolution ML penetrates through the surface of the target, and theinjection solution arrives at the inside thereof. Accordingly, it ispossible to achieve the object or purpose of the injection performed bythe syringe 20.

<Modified Embodiments of Igniter 10>

An explanation will be now made on the basis of FIG. 5 about a modifiedembodiment of the igniter 10. FIG. 5A shows an arrangement state of afirst member 1 and a second member 2 in a first modified embodiment.Note that the arrangement state shown in FIG. 5A is provided when theboth members are viewed in the direction of the axis of insertion intothe first member 1. In this context, in the first modified embodiment,the first member 1 has an inner surface including a cross section formedto be a regular octagon. The second member 2 is inserted into the spaceformed by the inner surface. Then, the second member 2 has an outersurface including a cross section formed to be a regular octagon in thesame manner as described above. Then, a space 7, in which the firstignition charge 8 can be accommodated, is formed between the innersurface of the first member 1 and the outer surface of the second member2 which are opposed to one another (in FIG. 5A, any illustration of thefirst ignition charge 8 is omitted).

In the case of the igniter 10 constructed as described above, as shownin FIG. 5A, the second member 2 is brought in contact with the innersurface of the first member 1. Therefore, the second member 2 cannot berotated freely. However, when such a state is given that the outersurface of the second member 2 is brought in contact with the innersurface of the first member 1 in accordance with the rotation, then thefirst ignition charge 8 is interposed between the both members, and thepredetermined pressure, which includes the shear force and thecompressive force, is intensively applied thereto. Therefore, the firstignition charge 8 can be efficiently ignited or inflamed. Thus, theoutput of the igniter 10 is easily utilized for a variety of purposes inthe same manner as in the first embodiment described above.

Next, an explanation will be made on the basis of FIG. 5B about a secondmodified embodiment of the igniter 10. FIG. 5B shows an arrangementstate of a first member 1 and a second member 2 in the second modifiedembodiment. Note that the arrangement state shown in FIG. 5B depicts thestate in cross section taken in the direction of the axis of insertioninto the first member 1 in the same manner as in FIG. 1. In thiscontext, in the second modified embodiment, the outer surface of thesecond member 2 is formed to have a circular truncated cone shape, andthe inner surface of the first member 1 is also formed to have acircular truncated cone shape corresponding thereto so that the secondmember 2 can be accommodated. Then, a space 7, in which the firstignition charge 8 can be accommodated, is formed between the innersurface of the first member 1 and the outer surface of the second member2 which are opposed to one another (in FIG. 5B, any illustration of thefirst ignition charge 8 is omitted).

Also in the igniter 10 constructed as described above, the firstignition charge 8 accommodated in the space 7 is ignited by rotating thesecond member 2 by the aid of the handle portion 6. In this arrangement,a stepped portion is formed at the connecting portion between the secondmember 2 and the handle portion 6 as shown in FIG. 5B, on account of thedifference between the diameter of the handle portion 6 and the diameterof the circular truncated cone surface of the second member 2. Further,a protrusion/recess portion 1 d, which corresponds to the steppedportion, is formed on the side of the first member 1. In this way, theseparation of the second member 2 from the first member 1 is regulatedby the engagement in the direction of the axis of insertion between thestepped portion disposed on the side of the second member 2 and theprotrusion/recess portion 1 d disposed on the side of the first member1. Accordingly, even when the pressure is applied to the second member 2on account of the combustion of the first ignition charge 8 and thesecond ignition charge 4, the second member 2 is prevented from beingseparated from the first member 1.

1. An igniter comprising: a first member having an inner surface; asecond member having an outer surface engaged with the inner surfacewhen in an assembled configuration and forming a space between the innersurface and the outer surface; and an ignition charge disposed in thespace, the second member being configured to move with respect to thefirst member when in the assembled configuration so as to apply apredetermined pressure, which includes a shear force and a compressiveforce, to the ignition charge to ignite the ignition charge.
 2. Theigniter according to claim 1, further comprising an openingcommunicating the space with an outside of the space.
 3. An ignitionmethod comprising: providing an ignitor having a first member and asecond member, the first member having an inner surface, the secondmember having an outer surface engaged with the inner surface andforming a space between the inner surface and the outer surface, anignition charge being disposed in the space; and applying a pressure,which includes a shear force and a compressive force, to the ignitioncharge to ignite the ignition charge.
 4. The method according to claim3, wherein applying the pressure comprises rotating one of the firstmember and the second member relative to the other one of the firstmember and the second member.
 5. A method of assembling an ignitor, themethod comprising: providing a first member having an inner surface;providing a second member having an outer surface; inserting the secondmember into the first member so as to form a space between the innersurface and the outer surface; and pouring an ignition charge when in aslurry form into the space, the ignition charge drying after beingpoured into the space so as to ignite when a predetermined pressure isapplied to the first member.
 6. The method according to claim 5, whereinthe first member comprises a first screw thread defining the innersurface, and wherein the second member comprises a second screw threaddefining the outer surface, and wherein inserting the second member intothe first member comprises engaging the second screw thread with thefirst screw thread.
 7. An igniter comprising: a first member having aninner surface; a second member having an outer surface engaged with theinner surface and forming a space between the inner surface and theouter surface when in an assembled configuration; and an ignition chargedisposed in the space, wherein one of the first member and the secondmember is configured to be moved relative to the other one of the firstmember and the second member when in the assembled configuration toignite the ignition charge by applying a predetermined pressure to theignition charge.
 8. The igniter according to claim 7, wherein thepredetermined pressure comprises a shear force and a compressive force.9. The igniter according to claim 7, wherein the outer surface of thesecond member is screw-engaged with the inner surface of the firstmember.